package com.skivingcloud.apiplatform.signature.util;

import javax.servlet.http.HttpServletRequest;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.regex.Pattern;

/**
 *  IP白名单校验
 *	白名单设计关键：
 *	包含多个规则，可以设计分隔符，分离规则字符串为多个规则列表，分割字符；，都可。
 *	单个ip，和多个ip白名单匹配规则，只要判断该规则中是否包含远端ip字符即可，实现简单如规则符：192.168.1.1；192.168.1.2
 *
 *	ip范围：范例规则字符-192.168.1.1-192.168.1.15
 *	即ip在 192.168.1.0/24 网段 1-15都为合法，默认为范围闭区间
 *
 *	设计思路：
 *	ipv4 分为4段，每段范围：0-255
 *	所以首先找出范围ip不同部分所在的段，然后依据ip划分规则，计算
 *
 *	例如 192.168.0.0-192.168.2.15
 *
 *	包含 网段 192.168.0.0 -192.168.0.255,192.168.1.0-192.168.1.255,192.168.2.0-192.168.2.15
 *	所以只要在这个范围中ip都是合法的
 *
 *	网段地址如何判断尼,请观察 网段地址规则,例如192.168.31.0/24
 *	网络地址/网络位数
 *	网络地址:192.168.31.0
 *	子网掩码:255.255.255.0
 *	测试ip:192.168.31.1
 *	网络地址=ip&子网
 *	所以判断一个ip是否属于一个网段可以通过ip和子网相与得到网络地址,如果和白名单中网络地址相同,则允许访问
 *
 */
public class IpWhiteCheckUtil {
    // IP的正则
    private static Pattern pattern = Pattern
            .compile("(1\\d{1,2}|2[0-4]\\d|25[0-5]|\\d{1,2})\\." + "(1\\d{1,2}|2[0-4]\\d|25[0-5]|\\d{1,2})\\."
                    + "(1\\d{1,2}|2[0-4]\\d|25[0-5]|\\d{1,2})\\." + "(1\\d{1,2}|2[0-4]\\d|25[0-5]|\\d{1,2})");
    private static final String DEFAULT_ALLOW_ALL_FLAG = "*";	// 允许所有ip标志位
    private static final String DEFAULT_DENY_ALL_FLAG = "0"; 	// 禁止所有ip标志位

    /**
     * Description: 获取访问的ip地址
     * @param request
     * @return
     */
    public static String getIpAddr(HttpServletRequest request) {
        String ip = request.getHeader("X-Forwarded-For");
        if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
            ip = request.getHeader("Proxy-Client-IP");
        }
        if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
            ip = request.getHeader("WL-Proxy-Client-IP");
        }
        if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
            ip = request.getHeader("HTTP_CLIENT_IP");
        }
        if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
            ip = request.getHeader("HTTP_X_FORWARDED_FOR");
        }
        if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
            ip = request.getRemoteAddr();
        }
        if ("0:0:0:0:0:0:0:1".equals(ip)) {
            ip = "127.0.0.1";
        }
        return ip;
    }

    /**
     * 根据IP白名单设置获取可用的IP列表
     * @param allowIp
     * @return
     */
    private static Set<String> getAvaliIpList(String allowIp) {
        String[] splitRex = allowIp.split(",");// 拆分出白名单正则
        Set<String> ipList = new HashSet<String>(splitRex.length);
        for (String allow : splitRex) {
            allow = allow.trim();
            if (allow.contains("*")) {// 处理通配符 *
                String[] ips = allow.split("\\.");
                String[] from = new String[] { "0", "0", "0", "0" };
                String[] end = new String[] { "255", "255", "255", "255" };
                List<String> tem = new ArrayList<String>();
                for (int i = 0; i < ips.length; i++)
                    if (ips[i].indexOf("*") > -1) {
                        tem = complete(ips[i]);
                        from[i] = null;
                        end[i] = null;
                    } else {
                        from[i] = ips[i];
                        end[i] = ips[i];
                    }

                StringBuilder fromIP = new StringBuilder();
                StringBuilder endIP = new StringBuilder();
                for (int i = 0; i < 4; i++)
                    if (from[i] != null) {
                        fromIP.append(from[i]).append(".");
                        endIP.append(end[i]).append(".");
                    } else {
                        fromIP.append("[*].");
                        endIP.append("[*].");
                    }
                fromIP.deleteCharAt(fromIP.length() - 1);
                endIP.deleteCharAt(endIP.length() - 1);

                for (String s : tem) {
                    String ip = fromIP.toString().replace("[*]", s.split(";")[0]) + "-"
                            + endIP.toString().replace("[*]", s.split(";")[1]);
                    if (validate(ip)) {
                        ipList.add(ip);
                    }
                }
            } else if (allow.contains("/")) {// 处理 网段 xxx.xxx.xxx./24
                ipList.add(allow);
            } else {// 处理单个 ip 或者 范围
                if (validate(allow)) {
                    ipList.add(allow);
                }
            }
        }
        return ipList;
    }

    /**
     * 	对单个IP节点进行范围限定
     * @param arg
     * @return 返回限定后的IP范围，格式为List[10;19, 100;199]
     */
    private static List<String> complete(String arg) {
        List<String> com = new ArrayList<String>();
        int len = arg.length();
        if (len == 1) {
            com.add("0;255");
        } else if (len == 2) {
            String s1 = complete(arg, 1);
            if (s1 != null)
                com.add(s1);
            String s2 = complete(arg, 2);
            if (s2 != null)
                com.add(s2);
        } else {
            String s1 = complete(arg, 1);
            if (s1 != null)
                com.add(s1);
        }
        return com;
    }

    private static String complete(String arg, int length) {
        String from = "";
        String end = "";
        if (length == 1) {
            from = arg.replace("*", "0");
            end = arg.replace("*", "9");
        } else {
            from = arg.replace("*", "00");
            end = arg.replace("*", "99");
        }
        if (Integer.valueOf(from) > 255)
            return null;
        if (Integer.valueOf(end) > 255)
            end = "255";
        return from + ";" + end;
    }

    /**
     *	 在添加至白名单时进行格式校验
     * @param ip
     * @return
     */
    private static boolean validate(String ip) {
        String[] temp = ip.split("-");
        for (String s : temp)
            if (!pattern.matcher(s).matches()) {
                return false;
            }
        return true;
    }

    /**
     * 	根据IP,及可用Ip列表来判断ip是否包含在白名单之中
     * @param ip
     * @param ipList
     * @return
     */
    private static boolean isPermited(String ip, Set<String> ipList) {
        if (ipList.isEmpty() || ipList.contains(ip))
            return true;
        for (String allow : ipList) {
            if (allow.indexOf("-") > -1) {// 处理 类似 192.168.0.0-192.168.2.1
                String[] tempAllow = allow.split("-");
                String[] from = tempAllow[0].split("\\.");
                String[] end = tempAllow[1].split("\\.");
                String[] tag = ip.split("\\.");
                boolean check = true;
                for (int i = 0; i < 4; i++) {// 对IP从左到右进行逐段匹配
                    int s = Integer.valueOf(from[i]);
                    int t = Integer.valueOf(tag[i]);
                    int e = Integer.valueOf(end[i]);
                    if (!(s <= t && t <= e)) {
                        check = false;
                        break;
                    }
                }
                if (check)
                    return true;
            } else if (allow.contains("/")) {// 处理 网段 xxx.xxx.xxx./24
                int splitIndex = allow.indexOf("/");
                // 取出子网段
                String ipSegment = allow.substring(0, splitIndex); // 192.168.3.0
                // 子网数
                String netmask = allow.substring(splitIndex + 1);// 24
                // ip 转二进制
                long ipLong = ipToLong(ip);
                //子网二进制
                long maskLong=(2L<<32 -1) -(2L << Integer.valueOf(32-Integer.valueOf(netmask))-1);
                // ip与和子网相与 得到 网络地址
                String calcSegment = longToIP(ipLong & maskLong);
                // 如果计算得出网络地址和库中网络地址相同 则合法
                if(ipSegment.equals(calcSegment))return true;
            }
        }
        return false;
    }

    /**
     * 	根据IP地址，及IP白名单设置规则判断IP是否包含在白名单
     * @param ip
     * @param ipWhiteConfig
     * @return
     */
    public static boolean isPermited(String ip, String ipWhiteConfig) {
        if (null == ip || "".equals(ip) || null == ipWhiteConfig)
            return false;
        //ip格式不对
        if(!pattern.matcher(ip).matches()) return false;
        if (DEFAULT_ALLOW_ALL_FLAG.equals(ipWhiteConfig))
            return true;
        if (DEFAULT_DENY_ALL_FLAG.equals(ipWhiteConfig))
            return false;
        Set<String> ipList = getAvaliIpList(ipWhiteConfig.replaceAll("，", ","));
        return isPermited(ip, ipList);
    }

    private static long ipToLong(String strIP) {
        long[] ip = new long[4];
        // 先找到IP地址字符串中.的位置
        int position1 = strIP.indexOf(".");
        int position2 = strIP.indexOf(".", position1 + 1);
        int position3 = strIP.indexOf(".", position2 + 1);
        // 将每个.之间的字符串转换成整型
        ip[0] = Long.parseLong(strIP.substring(0, position1));
        ip[1] = Long.parseLong(strIP.substring(position1 + 1, position2));
        ip[2] = Long.parseLong(strIP.substring(position2 + 1, position3));
        ip[3] = Long.parseLong(strIP.substring(position3 + 1));
        return (ip[0] << 24) + (ip[1] << 16) + (ip[2] << 8) + ip[3];
    }

    // 将10进制整数形式转换成127.0.0.1形式的IP地址
    private static String longToIP(long longIP) {
        StringBuilder sb = new StringBuilder("");
        // 直接右移24位
        sb.append(String.valueOf(longIP >>> 24));
        sb.append(".");
        // 将高8位置0，然后右移16位
        sb.append(String.valueOf((longIP & 0x00FFFFFF) >>> 16));
        sb.append(".");
        sb.append(String.valueOf((longIP & 0x0000FFFF) >>> 8));
        sb.append(".");
        sb.append(String.valueOf(longIP & 0x000000FF));
        return sb.toString();
    }
}
